#include <iostream>
#include<vector>
using namespace std;

int main() {
    int n;
    scanf("%d", &n);
    vector<vector<int>> dp(n + 1, vector<int>(n + 1));
    for (int i = 1;i <= n;i++)
    {
        for (int j = 1;j <= n;j++)
        {
            int tmp;
            cin >> tmp;
            dp[i][j] = dp[i - 1][j] + dp[i][j - 1] - dp[i - 1][j - 1] + tmp;
        }
    }
    int ret = -0x3f3f3f3f;
    for (int x1 = 1;x1 <= n;x1++)
    {
        for (int y1 = 1;y1 <= n;y1++)
        {
            for (int x2 = x1;x2 <= n;x2++)
            {
                for (int y2 = y1;y2 <= n;y2++)
                {
                    ret = max(ret, dp[x2][y2] - dp[x2][y1 - 1] - dp[x1 - 1][y2] + dp[x1 - 1][y1 - 1]);
                }
            }
        }
    }
    cout << ret;


    return 0;
}